Field of the Disclosure
The present disclosure relates to the fabrication of integrated circuits and to a process for forming a diamond like carbon layer with high etching selectivity, high film density and good mechanical strength on a substrate. More specifically, the disclosure relates to a process for manufacturing a diamond like carbon layer using electron beam plasma process to form the diamond like carbon layer with high etching selectivity, good mechanical strength, low stress and desired film transparency on a substrate for semiconductor applications.
Description of the Background Art
Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors and resistors on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density. The demands for faster circuits with greater circuit densities impose corresponding demands on the materials used to fabricate such integrated circuits. In particular, as the dimensions of integrated circuit components are reduced to the sub-micron scale, it is now necessary to use low resistivity conductive materials (e.g., copper) as well as low dielectric constant insulating materials (dielectric constant less than about 4) to obtain suitable electrical performance from such components.
The demands for greater integrated circuit densities also impose demands on the process sequences used in the manufacture of integrated circuit components. For example, in process sequences that use conventional photo lithographic techniques, a layer of energy sensitive resist is formed over a stack of material layers disposed on a substrate. The energy sensitive resist layer is exposed to an image of a pattern to form a photoresist mask. Thereafter, the mask pattern is transferred to one or more of the material layers of the stack using an etch process. The chemical etchant used in the etch process is selected to have a greater etch selectivity for the material layers of the stack than for the mask of energy sensitive resist. That is, the chemical etchant etches the one or more layers of the material stack at a rate much faster than the energy sensitive resist. The etch selectivity to the one or more material layers of the stack over the resist prevents the energy sensitive resist from being consumed prior to completion of the pattern transfer. Thus, a highly selective etchant enhances accurate pattern transfer.
As the geometry limits of the structures used to form semiconductor devices are pushed against technology limits, the need for accurate pattern transfer for the manufacture of structures having small critical dimensions and high aspect ratios has become increasingly difficult. For example, the thickness of the energy sensitive resist has been reduced in order to control pattern resolution. Such thin resist layers (e.g., less than about 2000 Å) can be insufficient to mask underlying material layers during the pattern transfer step due to attack by the chemical etchant. An intermediate layer (e.g., silicon oxynitride, silicon carbine or carbon film), called a hardmask layer, is often used between the energy sensitive resist layer and the underlying material layers to facilitate pattern transfer because of its greater resistance to chemical etchants. When etching materials to form structures having aspect ratios greater than about 5:1 and/or critical dimensional less than about 50 nm, the hardmask layer utilized to transfer patterns to the materials is exposed to aggressive etchants for a significant period of time. After a long period of exposure to the aggressive etchants, the hardmask layer without sufficient etching resistance may be changed in film properties, resulting in inaccurate pattern transfer and loss of dimensional control.
Furthermore, the similarity of the materials selected for the hardmask layer and the adjacent layers disposed in the film stack may also result in similar etch properties therebetween, thereby resulting in poor selectivity during etching. Poor selectivity between the hardmask layer and adjacent layers may result in non-uniform, tapered and deformed profile of the hardmask layer, thereby leading to poor pattern transfer and failure of accurate structure dimension control.
Additionally, relatively loose film structures (e.g., amorphous film structures) in the deposited film and/or hardmask layer may also result in low film mechanical strength and low hardness that result in the hardmask layer being unable to survive an entire etching process due to the attack of the aggressive etchants during the etching process. Insufficient film hardmask or film mechanical strength may adversely affect pattern transfer accuracy in the subsequent processes.
Therefore, there is a need in the art for an improved hardmask layer with desired film properties for subsequent lithography and etching processes.